49 CFR §196.103

1. (a)Use an available one-call system before excavating to notify operators of underground pipeline facilities of the timing and location of the intended excavation;
2. (b)If underground pipelines exist in the area, wait for the pipeline operator to arrive at the excavation site and establish and mark the location of its underground pipeline facilities before excavating;
3. (c)Excavate with proper regard for the marked location of pipelines an operator has established by taking all practicable steps to prevent excavation damage to the pipeline;
4. (d)Make additional use of one-call as necessary to obtain locating and marking before excavating to ensure that underground pipelines are not damaged by excavation.